In order to improve the energetic efficiency in internal combustion engines, in particular in vehicle applications, there are endeavors of utilizing heat energy, which is contained in the exhaust gas of the internal combustion engine. A possibility for utilizing the heat energy contained in the exhaust gas is the use of so-called thermoelectric generators, which can convert a temperature difference into an electric voltage or a heat flow into an electric current. Such thermoelectric generators operate according to the so-called Seebeck effect, which corresponds to an inversion of the so-called Peltier effect.
A thermoelectric generator usually consists of multiple individual thermoelectric elements, which can also be called thermoelectric modules and which in each case have a hot side and a cold side. By feeding heat to the hot side and by discharging heat on the cold side, a heat flow can be passed through the respective thermoelectric element which in the thermoelectric element is converted into an electric current. In order to be able to supply the hot side with heat and the cold side with cold a thermoelectric generator can be practically integrated in a heat exchanger, which comprises at least one heating channel for conducting a heating medium and at least one cooling channel for conducting a cooling medium. A thermoelectric generator is then arranged between such a heating channel and such a cooling channel so that the heating channel is located on the hot side of the respective thermoelectric generator and the cooling channel on the cold side of the respective thermoelectric generator. For this purpose, the heating channel, the thermoelectric generator and the cooling channel are stacked on top of one another in a stacking direction, thus forming a channel stack.
Such a thermoelectric element or such a thermoelectric module consists of a multitude of semiconductor elements, which convert a heat flow into an electrode flow and vice versa. In the respective thermoelectric element, multiple such semiconductor elements are usually connected in series. In particular, positively doped semiconductor elements, p-conductors in brief, and negatively doped semiconductor elements, n-conductors in brief, are connected in series alternating with one another. The electrical connection of successive p-conductors and n-conductors is usually effected by means of bridge elements, which preferably consist of a metal. Combined, this means that the respective thermoelectric element comprises a multitude of thermoelectrically acting semiconductor elements.
In the case of certain semiconductor materials, which within the respective thermoelectric element bring about the thermoelectric conversion, it can be required to protect these from contact with oxygen. To this end it is usual with conventional thermoelectric generators to hermetically encapsulate each individual thermoelectric element by itself. This encapsulation is effected with a type of casing or cover, which completely encloses and covers the respective thermoelectric element. Depending on the material of this casing or this cover, additional thermal resistance develops at this point which reduces the efficiency of the thermoelectric generator. A thermoelectric generator having multiple thermoelectric elements thus comprises multiple thermoelectric elements which are thus separately encapsulated each by itself, which in their encapsulation comprise multiple thermoelectric semiconductor elements each.